The Multimedia Over Coax Alliance (MoCA) standard supports networking (for example, home networking) over existing coaxial cable infrastructure. Devices, such as cable set top boxes, incorporating MoCA functionality can communicate over coaxial cable with other devices connected to a network.
MoCA uses adaptive constellation multi-tone (ACMT) modulation, which is a form of orthogonal frequency-division multiplexing (OFDM). OFDM is a frequency-division multiplexing (FDM) scheme used for digital modulation. The ACMT modulation scheme pre-equalizes the modulation-to-frequency response of each path using bit-loading—assigning bits efficiently based on subchannel quality, allowing more bits to be transmitted within higher quality subchannels and fewer bits to be transmitted within lower quality subchannels.
MoCA signals have preambles for frequency estimation, timing estimation, and channel estimation. To improve throughput efficiency, the MoCA 2.0 standard provides an option for reducing the channel estimation (CE) part of the preamble from two ACMT symbols to one ACMT symbol. However, this results in a modulation error ratio 3 dB higher than the actual signal to noise ratio. Further, even with two CE ACMT symbols, the channel estimation error will introduce a signal degradation of 1.8 dB.
Current technology for MoCA channel estimation is based on two channel estimation ACMT (OFDM) symbols, and the estimation therefore introduces 1.8 dB degradation. For the MoCA 2.0 standard, when only one CE symbol is available, the degradation will be as high as 3 dB. This will reduce the throughput and/or dynamic range of a MoCA network.
Systems and methods are needed for providing channel estimation of a burst OFDM signal, especially for burst OFDM signals having a large time variation from burst to burst and low channel quality (for example, as low as 5 dB).
Features and advantages of the present disclosure will become more apparent from the detailed description set forth below when taken in conjunction with the drawings, in which like reference characters identify corresponding elements throughout. In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The drawing in which an element first appears is indicated by the leftmost digit(s) in the corresponding reference number.